Confocal profilers have been developed to measure the surface height of smooth to very rough surfaces. The sample is scanned vertically in steps so that every point on the surface passes through the focus. The height of the surface at each pixel location is found by detecting the peak of the narrow axial response. Because only one or a few points of the surface are illuminated at the same time, in-plane raster scanning is also required in order to build up the axial response (i.e. the confocal image) at each vertical step. Confocal profiling provides the highest lateral resolution that may be achieved by an optical profiler. This makes it possible to reduce the spatial sampling, which is ideal for critical dimension measurements. High NA and magnification objectives are available to measure smooth surfaces with steep local slopes. The confocal profiler has extremely high light efficiency and an unlimited intrinsic measurement range. The proprietary confocal algorithms provide vertical repeatability on the nanometer scale. Super Long Working Distance (SLWD) objectives are also available to measure high aspect ratio features, large steps and steeply sloping samples. Step height measurements can also be made in structured or stratified samples containing dissimilar materials.